Precautions For Program Creation - Mitsubishi Electric FX5 User Manual
Melsec iq-f series
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*2 In the interlink mode, the PLC sets ER (DTR) to OFF when the amount of data already received becomes "Number of bytes to be
received -30", and asks the external equipment to stop sending. After this send request, the PLC can only receive up to 30 characters
and no more, so the external equipment temporarily stops sending, and then sends the remaining data after the ER (DTR) signal turns
ON again.
When sending is stopped, the receiving complete flag turns ON after the time-out check time and receiving completes.
When sending is not stopped, the PLC finishes receiving after it has received the final send data or 30 characters. Accordingly, make
sure that the amount of receive data is "30 + a".
Precautions for program creation
Using multiple RS2 instructions
The RS2 instructions can be used as many times as necessary in a program, but make sure that only one RS2 instruction is
driven in each serial port at a time. For switching of the RS2 instruction used, make sure the OFF time is longer than one scan
time.
Communication protocol setting
If protocol of communication settings (Page 136) for the channel to be used is not set to "Non-protocol Communication",
RS2 instructions cannot be used.
Using RS2 instruction together with another instruction
RS2 instruction cannot be used in the same serial port which is being used for any other communication (such as inverter
communication).
(Page 212 Combined Use of Serial Communication)
Control line interlink mode
In the interlink mode, set the amount of received data (n) to 31 or more. If it is set to 30 or less, the control line ER (DTR) is set
to OFF as soon as the PLC receives data.
Using RS-485 half-duplex, bi-directional communication
Be sure to check the following.
• Leave 100 s or more time between send completed start receive.
• Do not turn ON the sending request flag while receiving.
• Since data cannot be received while sending, do not send data from the counterpart equipment to the PLC.
• When using header or terminator, set before driving the RS2 instruction. Accordingly, do not change the setting while the
RS2 instruction is driven.
5 NON-PROTOCOL COMMUNICATION
5.7 Programming
5
153
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